example form class in Silex

controller.php

<?php

//somewhere in the controller
$form = $app["form.factory"]->create(new SzovegType());

SzovegType.php

<?php

namespace Insolis\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Validator\Constraints as Assert;

class SzovegType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add("content", "textarea", array(
            "label"         =>  "Szöveg",
            "constraints"   =>  array(
                new Assert\NotBlank(),
            ),

        ));
    }

    public function getName()
    {
        return "szoveg";
    }
}